摘要
评估膨胀土的膨胀行为对于膨胀土地区的结构设计十分重要。因降雨入渗,膨胀土在垂直方向和水平方向均产生膨胀变形,当膨胀变形受抑制时将产生膨胀压力,影响其周围结构的稳定性。为揭示膨胀土在增湿膨胀过程中出现各向异性的原因,从微观角度出发,通过电镜扫描(SEM)对百色中膨胀土和枝江弱膨胀土的微观结构进行观察,并通过图像处理技术统计分析膨胀土内黏土矿物颗粒的层状排列。通过研发的二维膨胀仪和改进的试件制备方法,从宏观角度测得了侧限条件下的两向膨胀规律。研究结果表明,膨胀土的微观结构呈片状且面-面相叠;当膨胀土处于天然松散状态时,其内部的黏土矿物颗粒随机定向排列且集聚;压实后,因受各向不均等应力作用,黏土矿物颗粒开始趋向于水平层状排列;干密度越大,土样越密实,其水平层状排列越显著。侧限条件下,两向的膨胀规律表现出显著的差异,干密度越大,膨胀性越强,这种差异就越明显。然而,对黏土矿物颗粒来说,其膨胀的方向垂直于其长轴,高度的水平定向是造成膨胀土在宏观上表现出膨胀各向异性的原因,这种两向的膨胀差异受到干密度和膨胀性的影响,难以做出预测,建议在工程实践中实测两向的膨胀规律。
Evaluation of swelling behavior is of great importance for designing structures in expansive soils areas.Due to infiltration,the expansive soil produces swelling deformation in both vertical and horizontal directions,and the swelling pressure occurs if the swelling deformation was restrained that influences the stability of surrounding structures.In order to reveal the causes of anisotropy behavior of expansive soil in the process of wetting and swelling,from the microscopic point of view,this paper observed the microstructure of expansive soil from Baise with medium swelling potential and Zhijiang with weak swelling potential respectively,and statistically analyzed the orientated distribution of clay mineral particles in expansive soil by image processing technique.Meanwhile,from macroscopic aspect,variations of swelling strain with swelling pressure were measured under lateral confining condition via the developed 2D dilatometer and the modified specimen preparation method.The results show that the microstructure of expansive soil is flaky and stacked layer by layer.When the expansive soil is of natural loose state,the clay mineral particles are randomly oriented and aggregated;After compaction,clay mineral particles tend to be horizontally oriented due to the anisotropic stress.The higher the dry density,the denser the soil sample,and the more obvious its horizontal orientation.Under lateral confined condition,significant swelling differences are observed between the vertical and horizontal direction.The greater the dry density,the stronger the swelling capacity,and the more obvious the difference.However,for clay mineral particles,the swelling direction is perpendicular to their long axis,so the highly horizontal orientation is the reason why expansive soil shows swelling anisotropy behavior in macroscopic view.The swelling anisotropy is influenced by dry density and swelling ability,which is difficult to estimate,therefore it is suggested to measure the swelling principle in two directions in engineering pra
作者
刘正楠
张锐
唐德力
刘昭京
周豫
LIU Zhengnan;ZHANG Rui;TANG Deli;LIU Zhaojing;ZHOU Yu(School of Traffic&Transportation Engineering,Changsha University of Science&Technology,Changsha 410114,P.R.China;China Railway Nanning Group Co.,Ltd.,Nanning 530029,P.R.China)
出处
《土木与环境工程学报（中英文）》
CSCD
北大核心
2024年第2期60-69,共10页
Journal of Civil and Environmental Engineering
基金
国家自然科学基金(51978085)
中国国家铁路集团有限公司科技研究开发计划(K2020G036,K2019G045)。
关键词
膨胀土
膨胀各向异性
微观结构
电镜扫描
膨胀试验
expansive soil
swelling anisotropy
microstructure
scanning electron microscope
swelling test
